For Zimmermann, it was his first session of the spring after having Tommy John surgery last summer. He threw 15 pitches -- all fastballs.

The trainers wanted Zimmermann to throw at 50 percent, but he threw the ball as hard as he could after the session started. Pitching coach Steve McCatty scolded Zimmermann for going full bore, but the misunderstanding didn't stop McCatty from praising Zimmermann for the way he looked on the mound.

"Jordan threw the ball very good," McCatty said. "We were trying to rope him in. He wanted to let it go. Chien-Ming was next to me. He looked at me when he said, 'Gas.' Jordan feels great and threw the ball great."

Zimmermann is ahead of schedule in terms of making a comeback, but general manager Mike Rizzo told Zimmermann that he would not pitch in a game until August. That's OK with Zimmermann, who is grateful to finally pitch on a mound.

"It was a pretty big deal, I guess, to step on a mound [for the first time in] seven months," Zimmermann said. "I didn't know where my first couple of balls were going to go, but they were right around the plate. I wasn't all over the placed, so that's good."